This invention relates generally to focusing projection displays including displays that may display computer information.
Projection displays may project an enlarged image on a display screen to be more easily viewable, for example, by a number of users. Projection display screens may also be mounted in housings with an image projected on one side of a screen, being viewed on the other side of the screen. In some cases, projection displays may be utilized as the displays for computer systems.
Room type projectors typically incorporate a motorized focus. Sometimes these projectors use remote control devices to enable the user to adjust the focus without having to return to the projector. However, the measurement of focal error is still a manual process, controlled by the operator.
High end slide projectors may include an autofocus feature. It has been empirically observed that the absolute location of the image plane varies from slide to slide. Thus, the focal plane of the lens varies as one gives a slide presentation. Instead of manually adjusting the focus for each slide, the projector adjusts the focus from slide to slide. While this produces a consistent result, current autofocus systems do not correctly focus each slide to account for the image plane of the slide. In other words, autofocus slide projectors still show out of focus, but consistently out of focus, slide shows. The burden remains on the operator to readjust for individual slide variations.
Thus, there is a continuing need for better autofocus systems for projection displays.
In accordance with one aspect of the present invention, a method of projecting images onto a display surface includes forming a first image. The first image is projected onto a display surface to form a second image. Information about the second image, reflected from the display surface, is received and information about the second image is compared to the information about the first image.